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Drilling into a concrete floor


Mirror Mirror

Question

Mirror Mirror

My house has an integral garage and I want to drill some holes in the concrete floor there to put in a ground anchor to lock my motorbike to.

I assume that the garage as well as the house will have a damp proof membrane. How far down will this be? The bolts are about 2 1/2” long, so if I drill holes like this, do you think it’s likely I’ll pierce the DPM?

I could attach it to the wall but it’s breezeblock which I assume would be easy to crowbar the mount away from?

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Green Devil

Cant you fix the anchors to the wall? Less hassle and no risk of going through the DPM in the floor. Once theres a hole there'll always be a hole and water will always head towards the hole.

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Definitely recommend using chemical fixings -almost guaranteed to work, as well as sealing potential.  Mechanical ground anchors in holes not quite the right size can have a nasty habbit of not grabbing but still being stuck down the hole, more likely if not used to fitting them.

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The concrete slab under my garage is about 6" thick.

The concrete slab under my house is about 4" thick.

The DPM is below the concrete.

If your garage is a relatively recent build then I would image its slab will be at least 4" thick.

If you use Chemical Fixings very liberally then even if you did puncture the DPM then the fixings would fill in the hole and prevent any water coming through the slab.

Please note that I am/was a Mechanical Engineer rather than a Civil Engineer.

 

 

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Bobthebuilder
3 minutes ago, Mirror Mirror said:

My house has an integral garage and I want to drill some holes in the concrete floor there to put in a ground anchor to lock my motorbike to.

I assume that the garage as well as the house will have a damp proof membrane. How far down will this be? The bolts are about 2 1/2” long, so if I drill holes like this, do you try ink it’s likely I’ll pierce the DPM?

Its possible you would go through the DPM. When you drill the holes stick a load of silicone in before the anchor bolts go in.

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On 26/04/2021 at 07:05, Green Devil said:

Cant you fix the anchors to the wall? Less hassle and no risk of going through the DPM in the floor. Once theres a hole there'll always be a hole and water will always head towards the hole.

You'd probably find it gets in your way, even on the floor it's amazing how often you trip over them. 

This might be a stupid question but are things like Stixall not worth considering? They won't be as good as polyester concrete but I'd imagine still rather strong.

IME the best is Pink Grip

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Bricks & Mortar

The drawing for your garage floor would have shown at least 4" of concrete.  Maybe 5 or 6".

The builders may have skimped a bit, and it could be as thinner in places.  2.5" is unlikely though, in a garage, unless they were total cowboys.  You'd have to expect the slab would crack badly if you park cars on that.

2nd for chemical anchor.  The type in the glass vial is best for casual use, since you don't need to buy a gun.  Just drill your hole.  Clean it out.  A bottle brush is good to loosen the dust, but then you need to get air to the bottom of the hole.  For dosboddian cheapskateness, a biro pen with the middle taken out, get your pen down in there, and blow!  Make sure to take a photo of your face afterward and post it.  (special blowout pump, compessed air, or a bicycle pump also possible, if you can get the tube down to the bottom of the hole).
Then just drop your glass capsule in, and force your fixing into the hole after it, breaking the capsule and squidging the goo around the threads.

There's a possibility, with chemical anchor, that you'd be repairing the dpm, in event you had punctured it.

https://www.screwfix.com/p/rawlplug-rcasv-resin-capsules-m12-12-x-110mm-drill-size-14mm-10-pack/7506f

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Dave Bloke

Be very careful. The floor should be reinforced concrete. If you use a powerful drill and it hits the reinforcing bar it can whip round and brake your wrist(s).

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Mirror Mirror
On 26/04/2021 at 08:05, Green Devil said:

Cant you fix the anchors to the wall? Less hassle and no risk of going through the DPM in the floor. Once theres a hole there'll always be a hole and water will always head towards the hole.

Thanks for the suggestion, but as I wrote in the OP, they are

just breezeblock which can be crumbly, and I think it would be easy to just crowbar them out of that.

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